Sensors & Transducers


Concentration measurement with process sensors

April 2022 Sensors & Transducers

To run chemical reactions in an optimal range and to control product quality, online concentration measurement is required. This ensures a fast intervention in case of concentration variation during production. Moreover, the concentration measurement reflects the quality of the products. For each chemical a specific method should be used, e.g. density, sound velocity and refractive index values which also strongly depend on the temperatures and concentrations of the substances. The highest measurement accuracies are necessary to calculate the exact concentration values. For the calculation of these values, concentration formulas are required. They can be developed based on the raw measurement.

It is crucial to find out which sensor or combination of sensors is best for measuring the concentration of chemical liquids in production, therefore, which sensor is ideal and what has to be considered? Concentration changes may have different effects on the density, sound velocity and refractive index of the liquids.

Density sensors

The L-Dens 7000 density sensor series represents the third generation of Anton Paar process density sensors for continuous monitoring of product quality. It consists of an oscillating U-tube, an excitation and pick-up system and two temperature sensors. The sensor electronics and the optional process instrumentation controller (Pico 3000) are built into the electronics housing of the sensor. The instrument has a modular design offering various interfaces (analog, digital and fieldbus) with a wide range of different process connections and wetted parts.

Sound velocity sensors

The L-Sonic sound velocity sensors for continuous monitoring of product quality consist of a fork or a tube including tall sensing elements. The sensor electronics and the optional process instrumentation controller (Pico 3000) are built into the electronics housing of the sensor. For many liquid solutions and mixtures, the sound velocity is directly proportional to the concentration. Therefore sound velocity measurement is an appropriate parameter to determine concentrations of solutions. The sound velocity can also be used for material characterisation.

Refractive index sensors

The L-Rix inline sensor determines the refractive index of liquids based on the critical angle measurement. The refractive index is a direct measure of the concentration. The measuring prism serves as the interface between L-Rix 5100 and the sample liquid. The light source illuminates the boundary layer between the prism and sample liquid. Depending on the angle, some light rays will be totally reflected, others only partially with the majority of the light refracted into the liquid. A CMOS array detects the reflected light and measures the critical angle. This angle is used to determine the refractive index (specified as nD) and to calculate the corresponding concentration.

Combined density and sound velocity sensors

L-Com 5500 is Anton Paar’s new density and sound velocity sensor combination in one instrument for the measurement of 3-component mixtures. It consists of an L-Dens 7500 density sensor with a piezo-excited U-tube which is expanded with a sound velocity module. Density and sound velocity values are directly calculated at the sensor electronics. It is ideal for the monitoring and controlling of chemicals such as formaldehyde-methanol-water mixtures or for the production control of beer.

Evaluation units

The mPDS 5 is a powerful evaluation unit for use with density, sound velocity and refractive index sensors. It combines the highest precision with ease of operation and robust design. mPDS 5 allows intuitive operation by a touchscreen user interface. It is a modular system equipped with boards for various inputs and outputs and accommodates the entire range of Anton Paar process sensors. Analog inputs are available for additional physical quantities such as conductivity, pH or pressure.

Pico 3000 is a high performance controller for the newest generation of Anton Paar process sensors. It is either installed in the electronics housing of the sensor or in the Pico 3000 RC housing for remote control. Different interfaces are available for communication. The modular design enables several configurations from simple analog output to high end communication via fieldbus. A simple and direct configuration of all values by a computer using the configuration software Pico 3000 Software is available.

Summary

When concentration measurement is required in a customer-specific process, it is important to choose the most suitable sensor. The question is: which sensor or combination of sensors ideally measures liquids in production? A large portfolio of sensor types and wetted parts allow multiple customer requirements to be fulfilled and provide flexible installation possibilities. Anton Paar also helps its customers to determine where the sensor should be installed and supports them throughout the installation of the high precision instruments or complete systems.

The company has a large database of concentration formulas for many different substances. Its experts can easily develop concentration formulas for new liquids/applications. Decades of experience in lab measurement as well as in process measurement provide the basis for tailormade solutions.

For more information contact Raymond Calitz, Anton Paar, +27 78 801 9319, raymond.calitz@anton-paar.com, www.anton-paar.com





Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Ultrasonic distance sensor
ASSTech Process Electronics + Instrumentation Sensors & Transducers
Wenglor’s new ultrasonic distance sensors combine low installation depth and easy integration of the sensor with tried and tested ultrasonic technology, setting new standards in terms of range and integration options.

Read more...
Grist for the mill
Turck Banner Editor's Choice Sensors & Transducers
To meet the requirements of Swiss company Bühler with regard to its MHSA grain huller, Turck certified its contactless Li linear position sensor for use in the Ex area. Thanks to its contactless operating principle, the robust sensors are both maintenance-free and wear-free. They offer an impressive performance due to their optimum reproducibility, resolution and linearity over a large temperature range.

Read more...
Ex-rated strain gauge transducer
Turck Banner Sensors & Transducers
Turck Banner's IMX12-SG for force measurement applications in hazardous areas achieves response times below 10 ms and can be used as a repeater or signal converter.

Read more...
Sensors for pulp and paper applications
Gail Norton Instrumentation Sensors & Transducers
Some of the toughest challenges for sensors are found in the pulp and paper industry. Here, high temperatures and a contaminated environment make it difficult for optical sensors to operate accurately ...

Read more...
Universal code reader for optimal reliability
Pepperl+Fuchs Sensors & Transducers
Camera-based code readers have already proven their worth in reading detailed data for automated processes, with the adaptability to suit many tasks.

Read more...
Working hand in hand to meet automotive OEMs’ strict requirements
Turck Banner Sensors & Transducers System Integration & Control Systems Design
The LASE Group, producer of machines and assembly cells for the automotive industry, places trust in its close collaboration with Turck Multiprox.

Read more...
2D vision sensor
ifm - South Africa Sensors & Transducers
Thanks to its integrated daylight filter, ifm’s new Dualis is highly resistant to extraneous light and boasts powerful algorithms to meet demanding requirements.

Read more...
3D machine vision camera gives robots human eyesight
SICK Automation Southern Africa Sensors & Transducers
The camera integrates easily into existing systems using system integration software, and features easily configurable input and output functionality.

Read more...
Draw-wire mechanisms for encoders
ifm - South Africa Sensors & Transducers
Adverse effects on distance detection, for example those caused by dirt in the case of optical distance measurement, are mostly eliminated.

Read more...
Position sensor for hydraulic cylinders
Instrotech Sensors & Transducers
SIKO’s SGH10 draw-wire encoder measures cylinder stroke precisely using Bowden cable sensor technology installed directly in the cylinder.

Read more...